To determine the minimum mass at which a water atmosphere remains stable, we fix a criterion derived from analytical considerations. Modeling the atmosphere beyond \(P_\mathrm {tr}\)  as a simple theoretical extended isothermal atmosphereGravity variation is taken into account. of temperature \(T_\mathrm {irr}\) , the pressure at infinity would be expressed as [1]}:
\(P_\infty = P_\mathrm {tr} \exp \left( - \frac{G M_\mathrm {p} m}{k T_\mathrm {irr} R_\mathrm {p}}\right),\) 
